An optical device is used as various illuminating devices or displays. Generally, it is necessary for the optical device to have a joining structure that joins different materials such as terminals and interconnections for transmission of an electrical signal that drives the optical element. For example, the organic EL element, which is an example of an optical element, includes a transparent electrode, another electrode that is disposed to face the transparent electrode, and an organic layer that is interposed between the electrodes. As a technology relating to the organic EL element, for example, there are technologies which are described in Patent Document 1 and Patent Document 2.
In the technology described in Patent Document 1, an electrode formed on a light-emitting function layer and a lead-out electrode that supplies a display signal to the electrode are fused and joined. Specifically, Patent Document 1 discloses a configuration in which a negative electrode that is constituted by a metal electrode layer, and a metal lead-out electrode layer are fused and joined at the connection portion through localized heating with laser light.
Patent Document 2 describes a light-emitting element including an electrode that is constituted by a metal line that is formed in a linear shape, and a polymer line that covers an upper surface and a lateral surface of the metal line.